things like mileage and MY might help.
or even 'has the coil ever been changed'?

my 98 xj 4.0L got a new coil for the hell of it at 100K miles. I change plugs every 30 K. and i do the cap and rotor about the same tme. wires last 2 caps or 60K.

by the condition of the air filtre and the darkness of the oil when i got the truck in aug ... i strongly doubt that the coil was changed , and with the condition of the sparks i really really doubt that they were changed .

and also , by changing the coil , it would be like changing the cap and wires if it had , right?? or would there be something else to change besides the coil and sparks?

Those ignition coils generally don't need to be replaced unless they are faulty. Most of the time new plugs will do it. I noticed the last time I did mine the rubber coil boots were wearing down, so I replaced them & now it runs like it did before. You can usually get them at any auto parts store, or you can go to the link I have below. Mine's an '02, but it should be the same thing for any wj. Also make sure you get the same champion plugs that it comes with, the cross reference number is under the hood on a large white sticker. I've seen bosch & other after market brands continue to throw misfire codes, especially if you go with anything other than the factory copper. Hope this helps you out.